1. Field of the Invention
The present invention relates to a BGA package having a half-etched bonding pad and a cut plating line and a method of fabricating the same. More particularly, the present invention pertains to a BGA package, in which a plating line is cut in a design step to form a predetermined uneven bonding pad using half-etching, thereby increasing the contact area between the bonding pad and a solder ball, assuring excellent surface properties and good drop test characteristics of the bonding pad, and a method of fabricating the same.
2. Description of the Related Art
An OSP (organic solderability preservative) surface treatment process is a technology capable of being used instead of conventional nickel/gold surface treatment, and may be used in cellular phones and portable electronic parts so as to realize excellent characteristics in a drop test. However, it is difficult to apply the OSP process, in which organics are applied on a copper pad, to conventional package processes. The reason for this is that an OSP layer on the copper pad is fatally damaged both thermally and physically while it is subjected to packaging steps, such as baking, wire bonding, die attach cure, and post mold curing, thus it is not easily removed by post flux in a solder junction process. Since this disadvantage forms a non-wetting zone on a solder surface and degradation of interface properties, it must be avoided. Recently, in order to avoid the above disadvantages, a half-etched copper pad is suggested before the OSP process, thereby improving properties of an OSP product. However, a severe chemical reaction, such as half-etching, depends on the design of a product.
FIG. 1 is a sectional view of a BGA package which is surface-treated using gold plating, according to the first embodiment of conventional technology.
As shown in FIG. 1, a circuit pattern 103a and a wire bonding pad pattern plated with gold 105a are provided on the upper side of an insulating layer 101, a chip 110 to be mounted is connected through wires 106 to a wire bonding pad, and a solder ball pad pattern including a circuit pattern 103b and a bonding pad plated with gold 105b is provided on the lower side of the insulating layer 101. A solder ball 107 is mounted on the ball pad. Furthermore, a through hole, for electrically connecting the upper and lower sides of the insulating layer 101 therethrough, is formed through the insulating layer 101.
With respect to this, the solder ball pad is surface-treated using the gold plating layer 105b. If the solder ball pad is surface-treated using the gold plating layer 105b, a plating line acts as an impedance in the formation of the gold plating layer 105b, thus electric properties are poor and undesirable characteristics, such as bending of a mold, occur. Additionally, undesirably, the solder ball is separated from the ball pad during a drop test.
To avoid the above problems, as shown in FIG. 2, OSP surface treatment is conducted.
FIG. 2 is a sectional view of a BGA package subjected to an OSP surface treatment process, according to the second embodiment of conventional technology.
As shown in FIG. 2, a circuit pattern 203a and a wire bonding pad pattern plated with gold 205 are provided on the upper side of an insulating layer 201, a chip 210 to be mounted is bonded through wires 207 to a wire bonding pad, and a solder ball pad pattern including a circuit pattern 203b and a bonding pad treated with OSP 206 is provided on the lower side of the insulating layer 201. A solder ball 208 is mounted on the ball pad. Furthermore, a through hole, for electrically connecting the upper and lower sides of the insulating layer 201 therethrough, is formed through the insulating layer 201.
However, as shown in FIG. 3, in a BGA package process using an organic solderability preservative (OSP), the organic solderability preservative (OSP) applied on the plating layer in which the solder ball pad is to be formed is thermally damaged during an in-line process or a back-end process. Particularly, it is thermally fatally damaged during a process of post mold curing (PMC) conducted at a high temperature of 175° C. or higher comprised in the back-end process.
In other words, as shown in FIG. 4, on the plating layer in which a bonding finger of the BGA package substrate or the solder ball pad is formed, as shown in a ball shear test, the organic solderability preservative (OSP), thermally damaged during the in-line process or the back-end process, remains.
In this regard, as shown in FIG. 5, when the solder ball is bonded to the plane copper plating layer 203b which is not vertically etched while the thermally damaged organic solderability preservative (OSP) 206 remains, the bonding area between the copper plating layer 203b and the solder ball 208 is reduced due to the remaining organic solderability preservative 206. Furthermore, the interaction of tin, which is contained in copper and the solder ball 208 constituting the copper plating layer 203b, with other metals is suppressed to interrupt the formation of intermetallic compound 1200 as shown in FIG. 6.
Accordingly, as shown in FIG. 6, the solder ball 208 is not attached to the copper plating layer 203b or easily separated therefrom by external impact, thus causing reduced reliability, such as formation of a non-wetting zone on a solder surface and degraded interface characteristics.